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SubjectRe: [net-next RFC V5 4/5] virtio_net: multiqueue support
On 07/05/2012 06:29 PM, Jason Wang wrote:
> This patch converts virtio_net to a multi queue device. After negotiated
> VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs,
> and driver could read the number from config space.
>
> The driver expects the number of rx/tx queue paris is equal to the number of
> vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
> optimization were introduced:
>
> - Txq selection is based on the processor id in order to avoid contending a lock
> whose owner may exits to host.
> - Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
> the queue pairs.
>
> Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---

...

>
> static int virtnet_probe(struct virtio_device *vdev)
> {
> - int err;
> + int i, err;
> struct net_device *dev;
> struct virtnet_info *vi;
> + u16 num_queues, num_queue_pairs;
> +
> + /* Find if host supports multiqueue virtio_net device */
> + err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
> + offsetof(struct virtio_net_config,
> + num_queues), &num_queues);
> +
> + /* We need atleast 2 queue's */


s/atleast/at least/


> + if (err || num_queues < 2)
> + num_queues = 2;
> + if (num_queues > MAX_QUEUES * 2)
> + num_queues = MAX_QUEUES;

num_queues = MAX_QUEUES * 2;

MAX_QUEUES is the limitation of RX or TX.

> +
> + num_queue_pairs = num_queues / 2;

...

--
Amos.


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